1. Field of the Invention
The invention relates in general to methods of remediating a contaminated site and of destroying contaminants.
2. Description of the Related Art
Currently steam is being used to clean up contaminated or remediation sites. FIGS. 9 and 10 show a common configuration of a current art treatment system, in this case the system used to clean up a NASA site at Cape Canaveral. Forming steam using electricity is expensive, so steam is commonly generated using a standard Heat Recovery Steam Generator (HRSG) unit. The generated steam is commonly injected into a delivery well, optionally with the addition of air. This delivers heat into the ground and down to various subsurface levels where the pollutants are located. This steam then passes through the soil toward separate vapor and ground water extraction wells. As it moves it mobilizes and removes a portion of the polluting or contaminant substances. The steam, or steam and air, are driven through the soil by the injection pressure, and optionally by a vacuum at the extraction wells. This vapor containing fluid and aqueous fluid carries with it various soil pollutants, as well as water which may contain dissolved components. As the fluid moves into the extraction wells, up to the surface and on to the treatment system, it can have gaseous and/or liquid phases.
The effluent fluid withdrawn from the extraction wells typically passes through a series of process steps to separate gaseous and liquid phases and to remove the pollution contents from the gaseous and liquid components. The removal of the pollution content is typically accomplished by incineration, but other purification processes can be used, instead, or in addition. The resulting purified fluids are then returned to the environment via the air, land, or water. The heat of combustion resulting from the incineration process is typically lost.
Normally the fluid is taken from the extraction well into a heat exchanger/condenser to cool it to below the dew point of the water before it passes into a water knock-out tank. This heat exchanger also requires a cooling tower and coolant transfer pump. After separation, the gaseous and liquid streams pass through a complex array of treatment devices.
Another practice in soil remediation is to produce steam, mix it with air and inject the mixture into the soil. The Final Report on the clean up of NASA's Cape Canaveral Launch Site 34, page 10, discusses this in a specific application:                “The rational for co-injection of air, based on published bench-scale and numerical modeling studies (Betz et al., 1998; Betz et al., 1997; Itamur, 1996; Kaslusky and Udell, 2002; Schmidt, et al. 1998) is that the mixture of steam and air creates a broader thermal front with a larger volume of air saturated with contaminant, thereby inhibiting condensation of the contaminant and formation of NAPL at the leading portion of the thermal front. The principle is that co-air injection produces an extended thermal front, spreading out the isotherms, to create a larger volume within which contaminants can be held in vapor. The air/steam mixture reduces the injection temperatures to the subsurface, and the co-injected air simultaneously increases the carrying capacity of contaminant in vapor. The optimal ratio of air to steam is based on expected concentration of contaminant, and the vapor pressure of the contaminant. Higher concentrations need greater volumes of air in order to have enough carrying capacity to inhibit condensation.”        
Another known process is referred to as recompression. This process uses a fluid to add further pressure to the injection well to force the wanted fluids to the extraction wells. This is often done with hot gas and/or steam which has been heated on the surface using a combustion system or by combusting a hydrocarbon fuel down within the well.
All of these technologies have one or more disadvantages such as complexity leading to reliability problems, high cost, and occupation of large areas. For example, producing the steam needed for the recompression process requires further equipment such as heat exchangers, pumps, compressors, with major quantities of energy needed operate this additional equipment. This increases operating and capital costs, and equipment footprints, while reducing efficiencies.
Thus, a need still exists for improvements in the art of decontamination of polluted sites, and safe disposal of the removed contaminants.